Prepare 120 ml of fresh espresso using high-quality beans and properly dialed grind size. Allow the espresso to cool to room temperature or slightly warm — never hot. Cooling preserves carbonation later and prevents the drink from tasting flat or overly bitter. For faster cooling, transfer the espresso to a shallow container or stir gently to release heat.

Fill a large pitcher or individual glasses generously with ice. Cold dilution is essential here — espresso tonic relies on temperature contrast and rapid chilling to achieve its clean, refreshing profile. Using insufficient ice results in a warm, aggressive drink with muted aromatics.

Pour the fully chilled tonic water into the ice-filled pitcher or glasses. Adding tonic first preserves carbonation structure and ensures proper dilution control. High-quality tonic should appear lively and effervescent with tight bubbles.

Slowly pour the cooled espresso over the back of a spoon or down the inside wall of the glass so it gently floats and partially layers over the tonic. This technique creates visual contrast and prevents immediate collapse of carbonation.

Give one very gentle stir only if desired — just enough to slightly combine the liquids while maintaining bubble structure. Garnish with lime peel twists and serve immediately while sharply cold and fully sparkling.